This study is performed to determine the optimal dose of DXM that, compared to placebo, decreases glucose excursions following an OGTT. Doses of 30 mg, 60 mg and 90 mg DXM were chosen. Since DXM 60 mg was effective in the previous study in increasing insulin secretion, this dose will be kept. A lower dose (30 mg) will be given to see whether effects on insulin secretion are present also at lower doses and then translate into a BG lowering action. A higher dose (90 mg) will be added to see whether this way an effect on glucose excursion reduction occurs following an OGTT, (like previously demonstrated with 270 mg DXM) that can be related to an increase of insulin secretion.